History

The network structure of our system has changed over the years. Broadly speaking it has changed from a Mainframe system to a distributed, network system.

In a mainframe system there's a central machine on which all the programs are run. In a typical distributed system, the programs are run on the machine the user is sat at - the users perhaps sharing resources like printers, etc. Each system has pros and cons

• A long time ago, the machine room was twice as big as it is today and contained an IBM Mainframe and stored files and ran programs.
• That was replaced by an HP fileserver plus HP terminals running HP-UX.
• The terminals proved too slow to run many programs, so we got some "CPU servers" to run programs, using the terminals merely to do input/output (i.e. they became "thin clients"). Each group of terminals connected to a CPU server was called a "cluster" - a term that we still use, though the meaning has changed.